The present invention relates to a chemical amplifying type positive resist composition used in the minute processing of a semiconductor.
In general, a lithography process using a resist composition has been adopted in the minute processing of a semiconductor. In lithography, the resolution can be improved with a decrease in wavelength of exposure light in principle as expressed by the equation of Rayleigh""s diffraction limited. A g-line with a wavelength of 436nm, an i-line with a wavelength of 365 nm, and a KrF excimer laser with a wavelength of 248 nm have been adopted as exposure light sources for lithography used in the manufacture of a semiconductor. Thus, the wavelength has become shorter year by year. An ArF excimer laser having a wavelength of 193nm is considered to be promising as a next-generation exposure light source.
A lens used in an ArF excimer laser exposure machine or an exposure machine using a light-source of shorter wave-length has a shorter lifetime as compared with lenses for conventional exposure light sources. Accordingly, the shorter time required for exposure to ArF excimer laser light is desirable. For this reason, it is necessary to enhance the sensitivity of a resist. Consequently, there has been used a so-called chemical amplifying type resist, which utilizes the catalytic action of an acid generated due to exposure, and contains a resin having a group cleavable by the acid.
It is known that, desirably, resins used in a resist for ArF excimer laser exposure have no aromatic ring in order to ensure the transmittance of the resist, but have an alicyclic ring in place of an aromatic ring in order to impart a dry etching resistance thereto. Various kinds of resins such as those described in Journal of Photopolymer Science and Technology, Vol. 9, No. 3, pages 387-398 (1996) by D. C. Hofer, are heretofore known as such resins. However, conventionally known resins have a problem that peeling off of a pattern tends to occur due to insufficient adhesion at development especially when the polarity is insufficient.
Journal of Photopolymer Science and Technology, Vol. 9, No. 3, pages 475-487 (1996) by S. Takechi et al., and JP-A-9-73173 reported that when a polymer or copolymer of 2-methyl-2-adamantyl methacrylate is used as a resin of a chemical amplifying type, 2-methyl-2-adamantyl is cleaved by an action of an acid to act as a positive type, and high dry etching resistance and high resolution as well as good adhesion to a substrate can be attained.
However, a resin having an alicyclic ring generally exhibits a high hydrophobicity and hence does not have a favorable affinity with a developer, which is an aqueous alkali.
On the other hand, a resin used in a resist for KrF excimer laser exposure usually is a polyvinylphenol resin wherein a part of the hydroxyl groups is protected by a group cleavable by an action of acid. In this case, resolution can be improved by raising the protection ratio. However, if the protection ratio is raised, hydrophobicity of the resin rises and its affinity with a developer deteriorates. When the hydrophobicity of the resin is high and the affinity with a developer is unsatisfactory, uniform development cannot be achieved with the result that the dimensional uniformity of a resulting pattern is affected or a development defect occurs.
An object of the present invention is to provide a chemically amplified positive resist composition containing a resin component and an acid generating agent which is suitable for use in excimer laser lithography utilizing ArF, KrF or the like, and is satisfactory in various resist performance characteristics such as sensitivity, resolution and adhesion to a substrate while exhibiting an excellent affinity (wettability) with respect to an alkali developer.
JP-A-10-274852 has reported that the use of a resin having a butyrolactone residue in part of a polymeric unit thereof for a chemically amplified positive resist composition improves the adherence of the resist composition to a substrate. Also, JP-A-11-305444has reported that the use of a resin having polymeric units derived from 2-alkyl-2-adamantyl (meth)acrylate and from maleic anhydride, respectively, for a chemically amplified resist composition improves the adherence of the resist composition to a substrate.
Further, JP-A-2000-137327 has described use of a resin having a polymeric unit derived from 2-alkyl-2-adamantyl (meth)acrylate and a polymeric unit derived from 3-hydroxy-1-adamantyl (meth)acrylate in a chemically amplified positive resist composition. Also, JP-A-2000-227658 has described use of a resin having a polymeric unit derived from hydroxystyrene and a polymeric unit derived from 3-hydroxy-1-adamantyl (meth)acrylate in a chemically amplified positive resist composition. The inventors of the present invention have conducted a further study based on these knowledge, and further discovered the fact that resolution and wettability with an alkali developer of a chemically amplified positive resist composition can be improved by using a resin containing a polymeric unit of high polarity as well as a polymeric unit of a specified adamantane structure. The present invention has been completed based on this discovery.
The present invention provides a chemically amplified positive resist composition comprising
a resin (X)
which, per se, is insoluble or slightly soluble in alkali but becomes soluble in alkali due to an action of acid, and has a polymeric unit (a) derived from 3-hydroxy-1-adamantyl(meth)acrylate and a polymeric unit (b) derived from xcex2(meth)acryloyloxy-xcex3-butyrolactone wherein the lactone ring may optionally be substituted by alkyl; and an acid generating agent (Y).